A conventional motor drive apparatus which combines a power circuit including a rectifying circuit for rectifying a.c. to d.c. and a means for suppressing harmonics in a power supply current with a motor drive circuit is described in JP-A Nos.6-105563 and 7-115788.
The conventional motor drive apparatus is provided with a converter circuit of power factor improvement type using a booster chopper circuit which executes suppression of harmonics in the power source current and d.c. voltage control simultaneously, and an inverter circuit which drives the motor, and the same executes its motor speed control by controlling its d.c. voltage and inverter conduction ratio.